Gas pressure regulators are used to control the pressure or flow of gas supplied from a gas supply such as a gas cylinder to a receptacle. In certain circumstances, it is important that gas flowing from the gas supply cylinder to the receptacle not be released into the surrounding atmosphere. One important example is in the supply of a fuel gas or an oxidising gas into a receptacle where there is a potential fire hazard in the surroundings.

During the transport of live aquatic life by aircraft, it is necessary to supply oxygen to the vessel containing the aquatic life. Conventional regulators used to supply oxygen to vessels containing aquatic life include vent openings so that, should the gas pressure regulator fail, pressure in the regulator will not build up to a point at which the regulator explodes or reaches such high temperatures as to be a fire hazard. The vent openings also function to balance diaphragms against changes in ambient pressure.

There are concerns surrounding the use of such gas regulators in aircraft transportation due to the possible leakage of gases that may increase the fire hazard In addition, in other applications where toxic gases are controlled in these-gas pressure regulators, there are also concerns for public health and safety.

It is an object of the present invention to provide a gas pressure regulator that does not have any gas

leakage to the external atmosphere, and in which no single component can fail in a manner which will allow the supplied gas to escape to the surrounding atmosphere.

According to the present invention there is provided a gas pressure regulator for regulating the flow of gas from a gas supply to a receptacle, including: -a regulator body including a gas inlet, a gas outlet and a gas passageway extending between said inlet and said outlet, -a first casing part coupled to the regulator body, and a first diaphragm interposed between said regulator body and said first casing part capable of restricting the flow of gas through one point along said gas passageway, -a second casing part coupled to the regulator body, and a second diaphragm interposed between said regulator body and said first casing part capable of restricting the flow of gas through a second point along said gas passageway, wherein the gas pressure regulator does not include any venting to the external atmosphere ; wherein the regulator body and each casing part is of sufficient strength to withstand the full pressure of gas supply, so that should one diaphragm fail, the regulator can continue to function without releasing gas to the atmosphere ; and wherein the gas passageway includes a restricted region which restricts flow through the regulator should the second diaphragm fail.

As will be explained in further detail below, in the event of failure of one diaphragm, the gas pressure regulator will continue to restrict the flow of gas through

the regulator to the receptacle to a certain extent, but not necessarily to the full extent initially set.

Accordingly, the term"function"as used above should not be read so restrictively as to refer only to normal operational functioning.

Preferably, the first diaphragm is upstream of the second diaphragm. Accordingly, the first diaphragm forms part of a first stage of the regulator, and the second diaphragm forms part of a second stage of the regulator.

Preferably, the restricted region is located between the second diaphragm and the gas outlet.

Preferably, the first diaphragm can be controlled to reduce the output pressure to a suitably low value such that, should the second diaphragm fail, gas flow through the regulator can be limited to a safe level by the first diaphragm and the restricted region. More preferably, the first diaphragm is pre-set to an appropriate position to reduce the output pressure at the first diaphragm to a suitably low value such that, should the second diaphragm fail, gas flow through the regulator can be limited to a safe level by the first diaphragm and the restricted region.

Preferably, the gas pressure regulator includes seals between adjacent elements of the device that prevent gas escaping to the external atmosphere, and the seals are each sufficiently strong to withstand the full supply pressure of the supply gas.

Preferably, the first and second casing parts comprise first and second bonnets.

Preferably, the first and second bonnets extend

axially of the regulator body. More preferably, the first and second bonnets extend from opposite axial ends of the regulator body. According to one particularly preferred embodiment, the bonnets are axially aligned.

Preferably, the first bonnet includes a first control means, and the second bonnet includes a second control means for controlling flow of gas through respective first and second points along the gas flow path.

Preferably, the first control means is adapted to be pre- set to reduce pressure to a preset level, and the second control means is adapted to be adjustable throughout operation of the regulator. For one example, the first control means may be in the form of a pre-setable adjusting screw, and the second control means can be in the form of a control knob adjusting screw. According to this particularly preferred embodiment, the device includes seals between the bonnets and the adjusting screws of sufficient strength to contain the full pressure of the gas supply.

Preferably, the maximum flow rate of gas through the gas pressure regulator is less than or equal to 5 litres per minute.

Preferably, the first control means is in the form of a pre-setable adjusting screw.

Preferably, the second control means is in the form of a control knob adjusting screw.

More preferably, the device includes seals between the bonnets and the adjusting screws of sufficient strength to contain the full pressure of the gas supply.

The present invention also provides for the use of a gas pressure regulator as described above in an

arrangement for the transportation of aquatic life.

Preferably the aquatic life is transported in an aircraft.

The present invention will now be described in further detail with reference to the drawings of a preferred embodiment of the invention in which: Figure 1 is a cross sectional view of the gas pressure regulator according to the preferred embodiment of the invention, and Figure 2 is a perspective view of an arrangement for transporting fish including the gas pressure regulator illustrated in Figure 1.

The gas pressure regulator 1 according to the preferred embodiment of the invention has two stages for regulating the pressure of gas flowing from a gas supply to a receptacle to which gas is required to be supplied. The first stage is upstream of the second stage. As used in the following description,"first"refers to an element in the first stage, and-second-refers to an element in the second stage.

The gas pressure regulator 1 includes a regulator body 2, and first and second casing parts in the form of first and second stage bonnets 3,4 respectively. These parts 2,3,4 are formed from brass, but could be made from other materials such as bronze, stainless steel or titanium. Aluminium components are not appropriate in this exemplified application due to the high fire hazard of aluminium components when used with a high pressure oxygen supply.

The first and second stage bonnets 3,4 are coupled to the regulator body 2 by any appropriate means.

According to the preferred embodiment illustrated, the first and second stage bonnets 3,4 include internally

screw-threaded ends adapted for mounting on to corresponding threaded regions of the regulator body 2.

The regulator body 2 also includes a gas inlet 5, a gas outlet 6, and a gas passageway 7 extending between the inlet and outlet 5,6. The gas passageway runs via a first stage diaphragm valve assembly 25 and a second stage diaphragm valve assembly 25. As used in the specification, it will be understood to persons skilled in the art that the term"diaphragm"is colloquially used to refer to a diaphragm valve or diaphragm valve assembly, as well as the actual diaphragm component of the valve. Accordingly, the term-diaphragm-should be interpreted to embrace those terms.

A gas supply, for example a gas cylinder, is connected to the gas inlet 5 via an inlet connector 8. The gas outlet is connected to a receptacle to which gas is required to be supplied. The gas pressure regulator of the present invention is particularly suitable for the supply of an oxygen-containing gas to a live aquatic life tank, which is to be transported by aircraft from one location to another. In this particular environment, it is not permissible, and indeed it can be very dangerous, for the oxygen-containing gas to escape or leak from the gas pressure regulator, or any other point between gas supply container and the receptacle.

Interposed between the regulator body 2 and the first stage bonnet 3 is a first diaphragm 9 of the first diaphragm valve assembly which is capable of restricting the flow of gas through a first stage of the gas pressure regulator, at a first location along the gas passageway.

The first diaphragm controls opening and closing the valve (not illustrated in detail) of the first diaphragm valve assembly to control flow of gas through the first stage.

This is done in the manner of a conventional diaphragm

valve. When there is a heavy demand on gas supply and the gas pressure on the face of the diaphragm falls significantly, the diaphragm spring pushes the valve wide open. When the demand for flow is reduced, the flow through the wide open valve causes the pressure on the face of the diaphragm to rise rapidly. The diaphragm is pushed away from the valve assembly, against the force of the regulator spring, and the valve closes down by the action of a light internal spring (not illustrated).

The first stage diaphragm is sealingly coupled to the regulator body. The seal of the first diaphragm 9 to the regulator body also provides a seal between the regulator body 2 and the first stage bonnet 3. The first stage bonnet 3 also includes a pre-setable adjusting screw 10. A seal is also provided between the pre-setable adjusting screw 10 and the first stage bonnet 3, in the form of a static seal 11.

The first stage bonnet does not include any venting to the external atmosphere. In contrast, all gas pressure regulators of the prior art commonly include venting in order to avoid potentially dangerous pressure build up in the regulator and to remove any back pressure on the diaphragm. The first stage bonnet 3 is also of sufficient strength to withstand the full pressure of the gas supply, so that should the first diaphragm 9 fail, gas will not escape from the first stage of the gas pressure regulator 1. In addition, the various seals between adjacent elements of the device that prevent gas escaping to the external atmosphere (ie. the seals between the regulator body 2 and the first stage bonnet 3, and between the first stage bonnet 3 and the pre-setable adjusting screw 10) are each of sufficient strength to withstand the full supply pressure of the supply gas. These features also contribute to the leakproof nature of the gas pressure regulator.

The pre-setable adjusting screw 10 is twisted to pre-load a first spring 17 to an appropriate value to reduce the output pressure of the first stage of the regulator to an appropriate level. Usually, the pre- setting of the pre-setable adjusting screw is done by the manufacturer as a static setting during manufacture, or prior to sale of the gas pressure regulator.

The gas pressure regulator also includes a second stage diaphragm 12 of the second diaphragm valve assembly interposed between the regulator body 2 and the second stage bonnet 4, capable of restricting the flow of gas through a second stage of the gas pressure regulator at a second location or point along the gas passageway. The second stage diaphragm 12 controls opening and closing of the valve 27 of the second valve diaphragm assembly to control flow of gas through the second stage in a similar manner to the first stage diaphragm.

The gas passageway 7 through the regulator body 2 includes an inter-stage passage section 13. The inter- stage passage does not include any venting, by means of a vent valve or any other feature, to the external atmosphere. The regulator body is also of sufficient strength to control the full supply pressure should the first diaphragm or the first stage of the gas pressure regulator fail.

Similarly to the first diaphragm 9, the second diaphragm 12 is sealingly coupled to the regulator body, and this seal also provides a seal between the regulator body 2 and the second stage bonnet 4. Adjustment of the second diaphragm 12 in the second stage of the gas pressure regulator 1 is controlled by a control knob adjusting screw 14. Twisting of the control knob changes the equilibrium location of the second diaphragm 12, and therefore the

output pressure of the second stage of the gas pressure regulator is modified. The control knob is of a type designed to be appropriate for operation during flow of gas through the gas pressure regulator 1.

A seal in the form of a sliding seal 15 is provided between the control knob adjusting screw and the second stage bonnet. This seal is of sufficient strength to retain the full gas supply should the second diaphragm 12 fail. The second stage bonnet 4 is also of sufficient strength to withstand the full supply pressure should the second diaphragm 12 fail.

In the region of the gas passageway 7 between the second diaphragm 12 and the gas outlet 6, there is provided a restricted region in the form of a fixed orifice 16. The fixed orifice 16 is of a size that would restrict the flow of gas through the regulator should the second stage diaphragm 12 fail.

In essence, the fixed orifice 16 sets a maximum flow of gas through the gas pressure regulator 1 in the event of failure of the second diaphragm 12. The actual maximum flow through the fixed orifice however will depend on the setting of the first stage diaphragm, since the actual flow level is dependent on the gas pressure.

Accordingly, reference to a maximum flow through the diaphragm should not be read narrowly so as to refer to a specific invariable maximum level.

The combination of features of the gas pressure regulator outlined above guard against any single component failure of the gas pressure regulator causing external leakage of the supplied gas.

In the event that the first diaphragm 9 fails, gas will not be able to leak through any region of the

first stage of the gas pressure regulator to the external atmosphere. In addition, the second stage is of sufficient strength to provide normal control of the full supply pressure passing to the second stage of the regulator.

Accordingly, the gas pressure regulator can continue to function without releasing gas to the atmosphere. It is to be understood, however, that the gas flow at the outlet port would be slightly lower than initially set with both the first and second diaphragms working. However, the gas pressure regulator does continue to function in the sense that it continues to control the flow of gas from the gas supply to the receptacle.

In order to be prepared to compensate for failure of the second stage diaphragm, the preset outlet pressure from the first stage is set to a lower than usual value.

By controlling the preset adjusting screw to this level, in the event of failure of the second stage diaphragm, the flow through the regulator is limited to an acceptable value by the fixed orifice 16 near the outlet port. In this instance, there will be no external leakage of the control gas to the external atmosphere, and the gas pressure regulator will continue to function in the sense that it prevents the full gas supply to be able to flow unhindered through the gas pressure regulator. Whilst the gas flow through the system will exceed the desired value, it will be restricted to an acceptable level, which is determined principally by the setting of the first stage diaphragm and the fixed orifice at the outlet port.

The various scenarios outlined above are summarised in the following table. Situation Leakage ? Flow Both stages OR No Normal operation First stage failure No Almost normal operation, but backup in event of failure of a stage no longer present Second stage failure No Flow constant, at acceptable value Both stages fail No Flow higher than required (no longer in range of normal operational flow), but not unrestricted.

According to the preferred embodiment of the invention, the gas pressure regulator is used in an arrangement 19 for the transportation of aquatic life from one location to another by air. The regulator can be incorporated into a wide variety of arrangements. The arrangement of one embodiment includes a gas cylinder 20 for supplying oxygen, the gas pressure regulator 1 illustrated in Figure 1, and a vessel 21 with a sealed lid containing water and the aquatic life, such as fish.

A low pressure oxygen supply line 22 leads from the gas pressure regulator 1. The vessel is also provided with a non-spill gas vent 22. These elements are all housed within a protective cover 23 on top of the lid of the vessel 21.

Many modifications may be made to the preferred embodiment illustrated without departing from the spirit and scope of the invention. For example, whilst the gas pressure regulator includes two stages, the gas pressure

regulator may be modified to incorporate a third stage, so as to provide a further back-up feature should any of the diaphragms of the gas pressure regulator fail.